Deep Learning models train really slow Jetson Nano
First of all, you mentioned that you installed the correct version of Tensorflow on Jetson. You can list the available Tensorflow devices with:



from tensorflow.python.client import device_lib
print(device_lib.list_local_devices())


And make sure that you see the GPU available. 

More importantly, Jetson Nano has a 128-core NVIDIA Maxwell™ architecture-based GPU. This might not be a powerful GPU for training a neural network with. As you can see here, in NVIDIA's official benchmark, they only tested trained models (i.e. classifications, object detections and segmentations). You can consider training your Keras model using another hardware and use it for labeling, classification, or etc. in your Jetson.